Multifunctional carbon layers design enabling high-performance micro-sized silicon anodes for advanced lithium-ion batteries.

The integration of micro-sized silicon (μm-Si) with high theoretical capacity and structurally stable graphite (Gr) has great potential in promoting the next generation of lithium-ion battery anodes. However, the application of Gr/μm-Si anodes is impeded by the excessive solid electrolyte interphase (SEI) accumulation and electrical disconnection caused by μm-Si swelling and fracturing. Herein, a multifunctional carbon layer (MCL) composed of in situ grown carbon nanotubes (CNTs) and pyrolytic carbon derived from polyacrylonitrile is prepared  to optimize Gr/μm-Si anode material. The pyrolytic carbon serves to anchor the CNTs and isolate the μm-Si surface from the electrolyte, mitigating side reactions and ensuring stable SEI formation. The CNTs create a robust three-dimensional conductive network, providing mechanical buffering for μm-Si volume expansion while enhancing electron and ion transport. Accordingly, the Gr/Si@MCL anode exhibits a discharge specific capacity of 503.6 mAh g^-1, maintaining an exceptionally low capacity decay of just 0.031% per cycle after 500 cycles at a current density of 1 A g^-1. Furthermore, the Gr/Si@MCL||LiFePO₄ full-cell demonstrates excellent performance, particularly with a high energy density of 347 Wh kg^-1. These results highlight the potential of the proposed structure design for advancing the practical deployment of Gr/μm-Si anodes in next-generation energy storage devices.